Removing the heat: Nanofluids promise efficient heat transfer

Next-breed of fluid may reform heat transfer

Article contributed by Mr. Mayank Bhola, Assistant Professor, Faculty of Technology and Computer Applications

Heat transfer isn’t the most usual topic of domestic talking. But if, on a hot summer day, your air conditioner breaks down or your car radiator boils over, it is immediately clear how critical it is to move heat efficiently from one place to another.

For decades, researchers have been working to develop more adequate heat transfer fluid to use in automobile engines and industrial machinery. Improved heat transfer of fluids like engine oil and coolants would help developing more powerful engines. These new engines would be smaller and are available to customer at low-cost, also minimum fuel demand will do less damage to the nature as it will generate less pollution.

Now, by using atoms on the smallest of scales, scientists have generated a next-breed of fluid that may reform heat transfer. By adding tiny ball-shaped particles to a traditional fluid, researchers can increase 40 % its ability to transfer heat.

Tiny means not larger than few nanometers — which is difficult to see with naked eyes (billionth of a meter). Steve Choi of Argonne’s Energy Technology Division and Jeff Eastman of the Argonne’s Materials Science Division developed these nanofluids. These nanofluids are generated by suspending materials like copper or copper oxide in liquids such as water or ethylene glycol (radiator fluid).

In initial trials researchers found that nanofluids can solve a number of problems for the heating, ventilation and air conditioning (HVAC) industry. Also their use could go past heat transfer in automobiles and manufacturing machinery. With progressing research, Choi and Eastman visualize nanofluids increasing the efficiency of high-heat generating applications like supercomputers and providing new cancer treatment techniques.

Scientists have been trying adding particles to fluids to increase thermal conductivity for a century, but the particle size had always remain a matter of trouble. Earlier, due to production restrains, engineers were only able to form microparticles — which are visible to the naked eye and with diameter thousand times greater than nanoparticles. These microparticles were so big that, like pebbels in a river, they can rapidly settle out of the fluid and sink to the bottom of a pipe or tank. If the fluid was kept rotating quickly to prevent such sinking, the microparticles may weaken the walls of the pipe, wearing them thin.

The difficulty faced by engineers was to create particles small enough that they would remain suspended for long periods of time, and also able to absorb high capacity of heat quickly.

Nanoparticle mysteries

Researchers have found that materials made up of nanoparticles are in contrast with their larger counterparts. They appear to be more strong and highly reactive. To enhance our understanding for the mysteries of nanoparticles, Argonne is preparing to create a station for nanoscale Materials to fabricate nanostructures and to examin their structural, physical and chemical properties.

Nanofluids research continues. Both scientists are working with other institutions to broaden their knowledge domain. To develop nanofluids for industry, Eastman has received a little Business Technology Transfer grant, associated with Nanopowder Enterprises of Piscataway, N.J. Argonne will test the thermal properties of the fluids the corporate produces. Choi is functioning through a cooperative research and development agreement with the Valvoline Co. to research the physical capabilities of nanofluids. He’s also collaborating with Purdue University and Rensselaer polytechnic to research the warmth transfer mechanism in nanofluids. Together, these efforts will allow Argonne researchers to develop a database of nanofluid properties and make accurate models of their behavior.

Manufacturers will need such information if nanofluids are to be developed for the market. One appealing possibility is to make fluids whose thermal properties are often engineered to specific tasks, but at now , basic facts about nanoparticles remain unclear.